Dishwasher leaves behind gritty residue i am not sure of what to try...

We have a Kitchen Aid dishwasher, 10 years old, never any problems until 2 weeks ago, then we started noticing a gritty subtance on the dishes and glassware. We're on well service, psi 40-60. water hardness is 6 grains. small trace of sulphur, and we have a Mermaid sulphur system, then a complete house carbon filter, and finally a Culligan water softner. Checked everything, Water temp. at kitchen was 120, all cycles on dishwasher were operating. Called in repair service, he says something is breaking down in the dishwasher, best to buy a new one. That'll be $150.00. Thank you very much. Tried the white vinegar, no change. Next bought 2 bottles of Dishwaser Magic. Slight improvement. Next bought 1 bottle of Finish Dishwasher Cleaner. Bingo. The thing is like brand new. even the trays slide in/out much easier. None of the dishsoaps contain phosphate, which is what helps disolve the minerals in the water. I'm not sure what the gritty stuff is, maybe the buildup over time, and it just keeps getting redistributed through the wash and rinse cycles, and finally baked on in the dry cycle. According to a tech with many years repairing appliances, the majority of their calls are for dishwasher poor performance, all because they removed the one compound that's been cleaning our dishes for years, Phosphate. We've always used Cascade gel soap. best on the market today, Finish Quantum. We tried it and dishes look terrific. It's a small tablet that fits in the soap dispenser. All Mfg's. today recommend that you run a dishwasher cleaner once a year, Experienced tech recommends every 3 months maybe more if you're on hard water. Good luck.

Hi the gritty residue is calcium. This builds up especially in hard water area's. Go to home depot and purchase a gallon of CLR or Lime away. Then set a pot and pan cycle, let the machine start to fill and then open the door and pour 1 pint of the de-liming solution into the dishwasher. Let the cycle run it's full course and then repeat this once a month for 3 months. The first treatment will clear the calcium and the next 3 will keep it clear. Use once every 6 months after. Mike